Optical analog display device

ABSTRACT

A bar of light conducting material has notches formed in its rear face. The size of the notches are inclined at progressively different angles so that the efficiency of reflection of light toward the front face progressively varies along the length of the bar. Light filters of different colors are placed at each end of the bar and a lamp is provided adjacent each filter so that colored light is transmitted through the bar from each end to illuminate the sides of the notches so that the display apparent at the front face of the bar is a series of striated colored images. The color reflected from a given notch is a function of the relative intensities of light from the lamps. An electrical sending unit responsive to some condition varies the intensity of each lamp according to the amplitude of the condition. Thus as the condition changes, the striated bands progressively change in color.

V IV" uruteu DUKES Herod et al.

[54] OPTICAL ANALOG DISPLAY DEVICE [72] Inventors: Donald M. Herod,Davison; John C. Engelman, Lapeer; William J. Johnston, Flint, all ofMich.

[731 Assignee: General Motors Corporation,

Detroit, Mich.

[221 Filed: Feb. 25, 1971 [21] Appl. No.: 118,846

[52] US. Cl. ..350/96 R, 240/1 EL [5 1] Int. Cl. ..G02b 5/14 [58] Fieldof Search ..350/96 R; 240/1 EL 56 References Cited UNITED STATES PATENTS2,591,864 4/1952 Peter et al ..350/96 R X Primary Examiner-David H.Rubin Attorney-Jean L. Carpenter, Paul Fitzpatrick and Warren D. Hill 13,692,383 1 Sept. 19, 1972 ABSTRACT A bar of light conducting materialhas notches formed in its rear face. The size of the notches areinclined at progressively different angles so that the efficiency ofreflection of light toward the front face progressively varies along thelength of the bar. Light filters of different colors are placed at eachend of the bar and a lamp is provided adjacent each filter so thatcolored light is transmitted through the bar from each end to illuminatethe sides of the notches so that the display apparent at the front faceof the bar is a series of striated colored images. The color reflectedfrom a given notch is a function of the relative intensities of lightfrom the lamps. An electrical sending unit responsive to some conditionvaries the intensity of each lamp according to the amplitude of thecondition. Thus as the condition changes, the striated bandsprogressively change in color.

3 Claims, 3 Drawing Figures OPTICAL ANALOG DISPLAY DEVICE This inventionrelates to an optical analog display device and particularly to abicolor display having no moving parts.

It is commonplace, as in automotive vehicles, for example, to monitorconditions such as temperature or liquid level by electrical means anddisplay the information by an electromechanical gage. Such gages arebulky and expensive.

It is therefore an object of this invention to provide an opticaldisplay device responsive to an electrical signal which is inexpensiveand compact.

It is another object of this invention to provide a bicolor analogdisplay.

It is a further object of this invention to provide an analog opticaldisplay device having no moving parts.

The invention is carried out by providing an elongated body of lightconducting material having a series of notches in the rear face andlight sources of different colors at each end of the body to internallyilluminate the surfaces of the notches so that the apparent colorreflected from each notch surface is a function of the relativeintensities of the light sources which vary according to a conditionbeing monitored. The invention further contemplates that the notches beformed to have a progressively variable efficiency of reflection foreach light source.

The above and other advantages of the invention will become moreapparent from the following specification taken with the accompanyingdrawings wherein like reference numerals refer to like parts andwherein:

FIG. 1 is a perspective view of the optical display device according tothe invention along with a schematic electrical circuit diagram of aliquid level sensor for operating the display device;

FIG. 2 is a plan view of a portion of the light conducting member of thedisplay unit of FIG. 1; and,

FIG. 3 is a front elevational view of the display unit of FIG. 1.

As illustrated in FIG. 1, the optical display device includes a bar oflight conducting material having a generally rectangular cross-sectionand enlarged at each end. By light conducting material is meant atransparent material which internally transmits light by the principleof total internal reflection. A suitable material is, for example, atransparent acrylic plastic. The enlarged ends of the bar 10 are coveredby colored light filters 12 and 14. The filter 12 preferably is red andthe filter 14 being green in color. Lamps 16 and 18 are positionedadjacent the filters for transmitting colored light therethrough intothe bar 10. The enlarged ends of the bar 10 provide a large area for theefficient collection of light from the lamps. Each lamp has one side ofits filament connected to a battery indicated as 8+ and the other sideconnected through lines 20 and 22 to an electrical transducer 24 whichis responsive to some condition which is desired to be monitored. In theexample of FIG. I, the transducer is a fuel level sensor and comprises apotentiometer 26 connected to the lines 20 and 22 having a groundedmovable tap 28 which moves in response to a fuel level float, not shown.When the fuel reservoir is filled, the movable tap 28 is at the lowerend of the potentiometer 26 and as the fuel supply diminishes, themovable tap 28 moves progressively toward the top of the potentiometer26.

The rear surface of the bar 10 contains a series of vertically extendingnotches 30. As best shown in FIG. 2, each notch defines an includedangle of about 45, however, the notches are each different from theother in that the inclination of the notch sides varies according to thedistance of the notch from the end of the bar 10. The extreme righthandnotch has its right side inclined at an angle of 45 to the rear face ofthe bar 10. The next notch has its right side inclined at an angle of505 with the rear face. The righthand slopes of the remaining notchesprogressively increase until finally the extreme lefthand notch has itsright face disposed at to the rear face. Where, as in the illustratedexample there are a total of nine notches, the increment of notchinclination varies by about 5.5 between notches. The left sides of thenotches are arranged in a manner identical to that of the right sideswith the extreme lefthand notch having a left surface inclined at 45 andthe left surface of the righthand notch being perpendicular to the rearface. The function of the notch faces is to reflect toward the front ofthe bar 10 light which is transmitted from either end of the bar. Thevarious inclinations of the notch sides determines the reflectionefficiency of each notch. Thus, the red light transmitted from the rightend of the bar is most efficiently reflected by the 45 surface of therighthand notch and will be progressively less efficiently reflected byeach of the succeeding notches. Similarly, the lefthand notch will mosteffectively reflect the green light from the left side of the bar. Evenif the notches were uniform, a similar but less marked effect wouldoccur since the light losses along the bar would cause the notchesfarther from the light source to be illuminated less well than thosenearer the light source.

In operation, when the sliding tap 28 is in its center positionindicating the fuel reservoir is half full, the lamps l6 and 18 willhave equal intensity. The resulting display as seen by an observerlooking at the front face of the bar 10 is depicted in FIG. 3. Astriated display having a band of light representing each of the notches30 will be visible. The bands represented by the hatched areas 32 willappear to be red while those represented by the hatched areas 34 willappear to be green. The central notch will be made up of a red and greenband showing a sharp line of demarcation and the right notches willappear to be red only while the left notches will appear to be greenonly. This display then as shown in FIG. 3 accurately indicates that thefuel reservoir is one-half full. Even though some red light is reflectedforward from the lefthand notches, the green light reflected therefromis dominant so that the eye discriminates between the two colors andsees only the dominant green light. Therefore, the lefthand bands willappear to be totally green and similarly the righthand bands will appearto be totally red. When the fuel reservoir is full and the moving tap 28is in its lowermost position, the lamp 18 will be at maximum intensitywhile the lamp 16 will be very dim. Then every light band on the displaywill appear to be green indicating a full reservoir. As the fuel leveldiminishes, the lamp 18 gradually becomes less intense while the lightfrom the lamp 16 becomes more intense. Then one by one the color bandswill change from green to red in progressive order until all of thebands will turn red when the fuel reservoir is empty or nearly so.

Of course, many other variations of the device will become apparent tothose skilled in the art to enable improvements or special designs ofthe optical display without departing from the principles of theinvention. For example, the size, number or shape of the notches mayvary. The shape of the bar may take other forms and obviously thefilters l2 and 14 may be arranged in other manners. It will be seen,however, that the optical display according to this invention providesan inexpensive, reliable, compact and easily read analog display.

The embodiment of the invention described herein is for purposes ofillustration and the scope of the invention is intended to be limitedonly by the following claims:

it is claimed:

1. An optical display device for providing a visual analog readout of acondition being monitored comprising an elongated body of transparentmaterial having a front and a rear face,

means for illuminating opposite ends of the body with light of differentcolors and variable intensity, the relative intensities of the lights ofeach color being a function of the condition, and a series of notches inthe rear face to provide angularly disposed light reflecting surfacesfor directing the light from each end toward the front face,

whereby the apparent color of light reflected from each notch toward thefront face depends upon the relative intensity of the light ofeachcolor.

2. An optical display device for providing a visual analog readout of acondition being monitored comprising an elongated body of transparentmaterial having a front and a rear face,

means for illuminating opposite ends of the body with light of differentcolors and variable intensity, the relative intensities of the lights ofeach color being a function of the condition, and a series of notches inthe rear face to provide angularly disposed light reflecting surfacesfor directing the light from each end toward the front face,

the reflecting surfaces facing one end being disposed at progressivelyincreasing angles relative to the rear face as the distance from the oneend increases and the reflecting surfaces facing the other end beingdisposed at progressively increasing angles relative to the rear face asthe distance from the said other end increases,

whereby the apparent color of light reflected from each notch toward thefront face depends upon the relative intensity of the light of eachcolor.

3. An optical display device for providing a bicolor visual analogdisplay of a condition being monitored comprising an elongated body oftransparent material having a front and rear face,

means at opposite ends of the body for internally illuminating the bodywith light of different colors and variable intensity, the relativeintensities of the lights of each color being a function of thecondition,

means comprising a series of reflectors formed in the rear fac f rreflectin the li ht of e ch color toward t e front face, are refle%tionefficiency of the reflectors progressively varying according to thedistance of each reflector from an end of the body, whereby the apparentcolor of light reflected from each reflector toward the front facedepends upon the relative intensity of the light of each color.

1. An optical display device for providing a visual analog readout of acondition being monitored comprising an elongated body of transparentmaterial having a front and a rear face, means for illuminating oppositeends of the body with light of different colors and variable intensity,the relative intensities of the lights of each color being a function ofthe condition, and a series of notches in the rear face to provideangularly disposed light reflecting surfaces for directing the lightfrom each end toward the front face, whereby the apparent color of lightreflected from each notch toward the front face depends upon therelative intensity of the light of each color.
 2. An optical displaydevice for providing a visual analog readout of a condition beingmonitored comprising an elongated body of transparent material having afront and a rear face, means for illuminating opposite ends of the bodywith light of different colors and variable intensity, the relativeintensities of the lights of each color being a function of thecondition, and a series of notches in the rear face to provide angularlydisposed light reflecting surfaces for directing the light from each endtoward the front face, the reflecting surfaces facing one end beingdisposed at progressively increasing angles relative to the rear face asthe distance from the one end increases and the reflecting surfacesfacing the other end being disposed at progressively increasing anglesrelative to the rear face as the distance from the said other endincreases, whereby the apparent color of light reflected from each notchtoward the front face depends upon the relative intensity of the lightof each color.
 3. An optical display device for providing a bicolorvisual analog display of a condition being monitored comprising anelongated body of transparent material having a front and rear face,means at opposite ends of the body for internally illuminating the bodywith light of different colors and variable intensity, the relativeintensities of the lights of each color being a function of thecondition, means comprising a series of reflectors formed in the rearface for reflecting the light of each color toward the front face, thereflection efficiency of the reflectors progressively varying accordingto the distance of each reflector from an end of the body, whereby theapparent color of light reflected from each reflector toward the frontface depends upon the relative intensity of the light of each color.